1. Field of the Invention
The present invention relates to a housing structure of vehicle-mounted electronic equipment for hermetically accommodating an electronic substrate between a set of cover and base and, more particularly, to a heat resistant, water resistant (waterproof) and vibration resistant housing structure suitable for mass-production.
2. Description of the Related Art
Hitherto, a housing structure is comprised of two pieces in which connectors are integrally formed into one body and an upper case (cover) made of resin, to which an electronic substrate is fixed, is adhesively fixed onto a lower case (base) with an adhesive sealant (see, for example, the Japanese Patent Publication (unexamined) No. 1999-346418).
In another example of conventional housing structure comprised of two pieces, an electronic substrate is accommodated in a housing formed of a case and a cover, and a heat generated by any heating part mounted on the electronic substrate is transferred to the cover and dissipated (see, for example, the Japanese Patent Publication (unexamined) No. 1996-148842).
In a further example, a fire retardant resin made of polybutyleneterephthalate resin mixed with glass fiber reinforcement is employed as vehicle-mounted electrical and electronic parts (see, for example, the Japanese Patent Publication (unexamined) No. 2000-178417).
With regard to heat dissipation from any heating part, a structure is known, in which a heat generated by any heating part fixed onto one face of a double-sided substrate is transferred to the other face via a through-hole-plated hole. The substrate is fixed onto a part of a heat-transfer housing through a heat-transfer elastic-insulating sheet (see, for example, Japanese Patent Publication (unexamined) No. 1996-204072).
In a still further example of a conventional structure, a heat generated by any heating part mounted on an electronic substrate is transferred to a cooling member such as aluminum base and dissipated (see, for example, the Japanese National Publication No. 2001-505000).
While improvement in dissipation of heat generated by the heating part becomes important under the background of highly miniaturizing and integrating the electronic substrate, vehicle-mounted electronic equipment is required to satisfy various requirements such as heat resistance, water resistance, vibration resistance, and mass-production.
However, in the above-mentioned Japanese Patent Publication (unexamined) No. 1999-346418, a problem exists in that the structure is not so constructed as to dissipate any heat generated by the heating part mounted on the electronic substrate.
Another problem exists in that it is not possible to obtain sufficient vibration resistance just by bonding the cover with the base and, moreover, heat resistance and sealing property of the finished products is not always sufficient.
In the structure of the above-mentioned Japanese Patent Publication (unexamined) No. 1996-148842, several problems exist in that any contact pressure is not sufficiently secured between the heating part and the cover, and the heat generated by a large number of heating parts is difficult to be dissipated. The entire structure is not sufficiently waterproof, either.